The invention relates to photography and more specifically, is directed to novel compounds which function as silver halide solvents and photographic products, processes and compositions which employ the compounds.
Photographic processing compositions capable of forming water-soluble complex silver salts are known to be useful in many types of siler halide photography. In conventional or "tray" development, it is customary to fix the developed silver halide emulsion by applying a solution of silver halide solvent, i.e., silver halide complexing agent which forms a water-soluble silver complex with the residual silver halide. The water-soluble silver complex thus formed and excess silver solvent are then removed from the developed and fixed emulsion by washing with water.
Silver halide solvents also have been employed in monobaths where a single processing composition containing a silver halide developing agent, in addition to the silver halide solvent, is utilized for both developing and fixing an exposed photosensitive silver halide layer. Silver halide solvents also have been employed in diffusion transfer photographic processes. Such processes are now well known in the art; see, for example, U.S. Pat. Nos. 2,543,181; 2,647,056; 2,983.606; etc. In processes of this type, an exposed silver halide emulsion is treated with a processing composition whereby the exposed silver halide emulsion is developed and an imagewise distribution of diffusible image-forming components is formed in the unexposed and undeveloped portions of the silver halide emulsion. This distribution of image-forming components is transferred by imbibition to an image-receiving stratum in superposed relationship with the silver halide emulsion to provide the desired transfer image. In diffusion transfer processes where a silver transfer image is formed, processing is effected in the presence of a silver halide solvent which forms a diffusible complex with the undeveloped silver halide. The soluble silver complex thus formed diffuses to the superposed image-receiving layer where the transferred silver ions are deposited as metallic silver to provide the silver transfer image. In preparing silver prints in this manner, the image-receiving element preferably includes a silver precipitating agent, for example, heavy metal sulfides and selenides as described in U.S. Pat. No. 2,698,237.
The present invention is directed to novel silver halide solvents and their use in photographic products, processes and compositions.